/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */
package com.feilong.lib.compress.archivers.zip;

import static com.feilong.lib.compress.archivers.zip.ZipConstants.BYTE_MASK;

import java.io.Serializable;
import java.math.BigInteger;

/**
 * Utility class that represents an eight byte integer with conversion
 * rules for the little endian byte order of ZIP files.
 * 
 * @Immutable
 *
 * @since 1.2
 */
public final class ZipEightByteInteger implements Serializable{

    private static final long               serialVersionUID   = 1L;

    private static final int                BYTE_1             = 1;

    private static final int                BYTE_1_MASK        = 0xFF00;

    private static final int                BYTE_1_SHIFT       = 8;

    private static final int                BYTE_2             = 2;

    private static final int                BYTE_2_MASK        = 0xFF0000;

    private static final int                BYTE_2_SHIFT       = 16;

    private static final int                BYTE_3             = 3;

    private static final long               BYTE_3_MASK        = 0xFF000000L;

    private static final int                BYTE_3_SHIFT       = 24;

    private static final int                BYTE_4             = 4;

    private static final long               BYTE_4_MASK        = 0xFF00000000L;

    private static final int                BYTE_4_SHIFT       = 32;

    private static final int                BYTE_5             = 5;

    private static final long               BYTE_5_MASK        = 0xFF0000000000L;

    private static final int                BYTE_5_SHIFT       = 40;

    private static final int                BYTE_6             = 6;

    private static final long               BYTE_6_MASK        = 0xFF000000000000L;

    private static final int                BYTE_6_SHIFT       = 48;

    private static final int                BYTE_7             = 7;

    private static final long               BYTE_7_MASK        = 0x7F00000000000000L;

    private static final int                BYTE_7_SHIFT       = 56;

    private static final int                LEFTMOST_BIT_SHIFT = 63;

    private static final byte               LEFTMOST_BIT       = (byte) 0x80;

    private final BigInteger                value;

    public static final ZipEightByteInteger ZERO               = new ZipEightByteInteger(0);

    /**
     * Create instance from a number.
     * 
     * @param value
     *            the long to store as a ZipEightByteInteger
     */
    public ZipEightByteInteger(final long value){
        this(BigInteger.valueOf(value));
    }

    /**
     * Create instance from a number.
     * 
     * @param value
     *            the BigInteger to store as a ZipEightByteInteger
     */
    public ZipEightByteInteger(final BigInteger value){
        this.value = value;
    }

    /**
     * Create instance from bytes.
     * 
     * @param bytes
     *            the bytes to store as a ZipEightByteInteger
     */
    public ZipEightByteInteger(final byte[] bytes){
        this(bytes, 0);
    }

    /**
     * Create instance from the eight bytes starting at offset.
     * 
     * @param bytes
     *            the bytes to store as a ZipEightByteInteger
     * @param offset
     *            the offset to start
     */
    public ZipEightByteInteger(final byte[] bytes, final int offset){
        value = ZipEightByteInteger.getValue(bytes, offset);
    }

    /**
     * Get value as eight bytes in big endian byte order.
     * 
     * @return value as eight bytes in big endian order
     */
    public byte[] getBytes(){
        return ZipEightByteInteger.getBytes(value);
    }

    /**
     * Get value as Java long.
     * 
     * @return value as a long
     */
    public long getLongValue(){
        return value.longValue();
    }

    /**
     * Get value as Java BigInteger.
     * 
     * @return value as a BigInteger
     */
    public BigInteger getValue(){
        return value;
    }

    /**
     * Get value as eight bytes in big endian byte order.
     * 
     * @param value
     *            the value to convert
     * @return value as eight bytes in big endian byte order
     */
    public static byte[] getBytes(final long value){
        return getBytes(BigInteger.valueOf(value));
    }

    /**
     * Get value as eight bytes in big endian byte order.
     * 
     * @param value
     *            the value to convert
     * @return value as eight bytes in big endian byte order
     */
    public static byte[] getBytes(final BigInteger value){
        final byte[] result = new byte[8];
        final long val = value.longValue();
        result[0] = (byte) ((val & BYTE_MASK));
        result[BYTE_1] = (byte) ((val & BYTE_1_MASK) >> BYTE_1_SHIFT);
        result[BYTE_2] = (byte) ((val & BYTE_2_MASK) >> BYTE_2_SHIFT);
        result[BYTE_3] = (byte) ((val & BYTE_3_MASK) >> BYTE_3_SHIFT);
        result[BYTE_4] = (byte) ((val & BYTE_4_MASK) >> BYTE_4_SHIFT);
        result[BYTE_5] = (byte) ((val & BYTE_5_MASK) >> BYTE_5_SHIFT);
        result[BYTE_6] = (byte) ((val & BYTE_6_MASK) >> BYTE_6_SHIFT);
        result[BYTE_7] = (byte) ((val & BYTE_7_MASK) >> BYTE_7_SHIFT);
        if (value.testBit(LEFTMOST_BIT_SHIFT)){
            result[BYTE_7] |= LEFTMOST_BIT;
        }
        return result;
    }

    /**
     * Helper method to get the value as a Java long from eight bytes
     * starting at given array offset
     * 
     * @param bytes
     *            the array of bytes
     * @param offset
     *            the offset to start
     * @return the corresponding Java long value
     */
    public static long getLongValue(final byte[] bytes,final int offset){
        return getValue(bytes, offset).longValue();
    }

    /**
     * Helper method to get the value as a Java BigInteger from eight
     * bytes starting at given array offset
     * 
     * @param bytes
     *            the array of bytes
     * @param offset
     *            the offset to start
     * @return the corresponding Java BigInteger value
     */
    public static BigInteger getValue(final byte[] bytes,final int offset){
        long value = ((long) bytes[offset + BYTE_7] << BYTE_7_SHIFT) & BYTE_7_MASK;
        value += ((long) bytes[offset + BYTE_6] << BYTE_6_SHIFT) & BYTE_6_MASK;
        value += ((long) bytes[offset + BYTE_5] << BYTE_5_SHIFT) & BYTE_5_MASK;
        value += ((long) bytes[offset + BYTE_4] << BYTE_4_SHIFT) & BYTE_4_MASK;
        value += ((long) bytes[offset + BYTE_3] << BYTE_3_SHIFT) & BYTE_3_MASK;
        value += ((long) bytes[offset + BYTE_2] << BYTE_2_SHIFT) & BYTE_2_MASK;
        value += ((long) bytes[offset + BYTE_1] << BYTE_1_SHIFT) & BYTE_1_MASK;
        value += ((long) bytes[offset] & BYTE_MASK);
        final BigInteger val = BigInteger.valueOf(value);
        return (bytes[offset + BYTE_7] & LEFTMOST_BIT) == LEFTMOST_BIT ? val.setBit(LEFTMOST_BIT_SHIFT) : val;
    }

    /**
     * Helper method to get the value as a Java long from an eight-byte array
     * 
     * @param bytes
     *            the array of bytes
     * @return the corresponding Java long value
     */
    public static long getLongValue(final byte[] bytes){
        return getLongValue(bytes, 0);
    }

    /**
     * Helper method to get the value as a Java long from an eight-byte array
     * 
     * @param bytes
     *            the array of bytes
     * @return the corresponding Java BigInteger value
     */
    public static BigInteger getValue(final byte[] bytes){
        return getValue(bytes, 0);
    }

    /**
     * Override to make two instances with same value equal.
     * 
     * @param o
     *            an object to compare
     * @return true if the objects are equal
     */
    @Override
    public boolean equals(final Object o){
        if (o == null || !(o instanceof ZipEightByteInteger)){
            return false;
        }
        return value.equals(((ZipEightByteInteger) o).getValue());
    }

    /**
     * Override to make two instances with same value equal.
     * 
     * @return the hashCode of the value stored in the ZipEightByteInteger
     */
    @Override
    public int hashCode(){
        return value.hashCode();
    }

    @Override
    public String toString(){
        return "ZipEightByteInteger value: " + value;
    }
}
